The opening episode's six groups include a cappella group All The King's Men; Polish jazz group Alle Choir; the London International Gospel Choir; female vocal soul group Songbird Sessions; Welsh choir Sgarmes; and 4 Tune Tellers and Kimmy. To progress, they must impress judges Gareth Malone, Kelis and Bebe Rexha. The programme opens with a musical mash-up arranged by Deke Sharon. Groups then go head to head in a series of knockout choral challenges. First they each perform their showstopper before battling it out with their opponent in a themed riff-off. The judges then decide which group goes through to the solo battles. At the end only two groups remain, where they must face the final battle. Here they share the same song, before Bebe Rexha joins in with the group the judges have chosen to go through to the final.